Regarding tools which machine the peripheral edge of a hole bored by a drilling tool (such as a drill), PCT Japanese Translation Patent Publication No. 2004-524979 (“JP '979”), Japanese Unexamined Patent Application Publication No. 2006-43868 (“JP '868”), and Japanese Unexamined Patent Application Publication No. 2003-117711 (“JP '711”) show a type of ring with a cutting edge as an example, in which a cutting edge tip for machining the peripheral edge of the hole is attached to a ring portion fixed to the drilling tool. In this ring with a cutting edge, the peripheral edge of the hole can be machined before the drilling tool is pulled out of the hole. Thereby, both operations, boring a hole and machining its peripheral edge, can be efficiently performed.
As this convention type of ring with a cutting edge, JP '979 teaches one example in which the ring with a cutting edge is fastened and fixed to the surface of a chip discharge groove (twist groove) of a drilling tool located at the inner peripheral side of a fastening ring, by a fastening screw going through a ring portion in its radial direction. In this case, a fastening shoe is provided between the fastening screw and the chip discharge groove (twist groove).
Further, as one conventional ring with a cutting edge, JP '868 teaches one example in which the ring with a cutting edge is constituted by two divided bodies divided into two in the peripheral direction of a ring portion, and the divided bodies are fastened together by screws. In this case, the inner diameter of the ring portion is required to be smaller (for example, −1.0 to 0.0 mm) than the outer diameter of the drill.
Moreover, as another conventional ring with a cutting edge, JP '711 teaches one example in which a slit is formed in one place in the peripheral direction of a ring portion, and this tool is fastened by screws such that the width of the slit becomes smaller and thereby fixed to a drilling tool.
However, two or more of twisted chip discharge grooves are formed in a normal drill. Therefore, in the ring with a cutting edge described in JP '979, it is necessary to operate two or more of fastening screws for fixing the ring with a cutting edge to the drill. Thus, there is a problem in that the operation for attaching is with some trouble. Moreover, since the ring with a cutting edge described in JP '979 is fixed to the drill via the fastening shoe, there is a possibility that the central axes of the drill and the ring with a cutting edge may be largely off each other. Further, in the ring with a cutting edge described in JP '868 and JP '711, the ring portion is fastened and fixed by screws such that the gap between the two divided bodies and the width of the slit may become smaller. Therefore, there is a problem in that the ring portion easily rotates when the screws are operated, and the operation for attaching this tool is also with some trouble.
This invention aims at providing a ring with a cutting edge which is easily attachable to a drilling tool.